The present invention relates generally to coating compounds containing aqueous polyolefin dispersions. In particular, at least in some embodiments, the coating compounds of the present invention may be useful for coating woven carpets.
Generally speaking, woven carpets may be produced on a loom similar to how a woven cloth is produced. Coatings can be applied to either the front side or the back side of the carpet to enhance certain properties. For instance, to provide adhesive bonding, a coating compound may be applied to the carpet. Among other things, the coating compound may bond the warp and weft yarns in the woven carpet. Typical coating compounds include latex, urethane, or vinyl systems, with latex being most common. Examples of typical latexes that may be used are carboxylated styrene-butadiene (“SB”) or acrylate latex adhesives. Conventional latex systems are low-viscosity, aqueous compositions that can be applied at high carpet production rates. The carpet typically passes through an oven that dries the latex on the carpet. The coating compound may be applied as a single coating or layer or as a multiple layered system.
As the use of polyolefin fibers in carpets has become more popular, the use of carboxylated SB and acrylate-based latex coating compounds on a polyolefin substrate has presented challenges. This is believed to be due, at least in part, to the relative incompatibility of the apolar polyolefin fibers and the more polar polymer in the coating compound. This incompatibility is believed to result in weak associations between the fibers and the latex coating compounds. One of the practical results of this is an increased incidence of carpet fraying. When carpet is manufactured, it has a raw edge that if it is not protected will fray. Although this fraying phenomena can also be observed with naturals yarns (like jute and cotton) or relative polar polymer yarns (like nylon and polyester), most fraying occurs as a result of the combination of apolar yarns (like polypropylene and other polyolefin copolymers) and carboxylated SB- and acrylate-based latex coating compounds.
To combat these problems with latex coating compounds, polyolefin-based coating compounds have become more prevalent. Additionally, those in the art have tried to combat the fraying problems by controlling the degree of yarn coverage. The degree of yarn coverage in the woven fabric is controlled by three parameters: wetting ability, viscosity, and applied dry coat weight. Another technique to protect the edge of the carpet against fraying has involved application of a serge strip on the edge of the carpet.